1. Field of the Invention
The present invention relates to fluid separation systems and/or methods. Particular examples include separation systems and/or methods for blood component processing and/or preparation. Such separation systems and/or methods may take place in a centrifuge of a type, which may generally have a rotor with an annular separation compartment and a substantially open central compartment that may be arranged generally concentrically about the axis of rotation of the rotor.
2. Description of the Related Art
Today's blood centers face formidable challenges. Doctors, hospitals and blood banks demand greater quantities and more specific and higher quality blood component products for the patients they serve. An optimal general solution is to maximize the quantity and the quality of blood components processed from each collection.
A review of conventional blood processing reveals that in the preparation of blood component products, blood is often separated into one or more components such as plasma, a buffy coat and/or platelets and red blood cells by centrifugation. Conventional so-called manual and apheresis (automated separation) processes are both used. However, since the present invention is generally directed to processing manually collected discrete portions or units of whole blood, and since apheresis has taken on the general meaning that it avoids this initial step of manual collection of one or more discrete units of whole blood, conventional apheresis as a general process will not be discussed further here.
In conventional manual collection processes, a sterile set of interconnected flexible containers or bags is typically used. The presently most common mode of operation is to use a sterile set of interconnected substantially rectangular blood bags, one bag being the initial collection container and often also the separation container, into which whole blood is collected. The other interconnected bags are then the resulting processed blood component containers, to which the separated components are transferred after processing/separation. The entire set is typically centrifuged in a swing-out centrifuge bucket or cup and, during centrifugation, the separating and separated blood components form layers in the separation container according to the respective increasing specific weights. A plasma layer, a buffy coat layer and a layer of red blood cells are thus formed, and these usually remain stratified even after centrifugation is complete. Then in this conventional process, the set of bags is typically manually removed from the centrifuge and moved to a pressing or expresser device for expressing or pressing out the plasma layer and/or the red blood cell layer to associated interconnected component containers. This would then usually leave the buffy coat layer in the original bag or, the buffy coat could also be expressed to its own interconnected container or otherwise to a pooling container. Great care must be used during the manual handling of the bags when the layers are separated/stratified in this manner, yet still in contact with each other in the original separation bag, because such manual handling often results in some undesirable re-mixing of the components which would then result in a lower quality product or an inefficiency in the overall process by necessitating a re-centrifugation of that unit of blood.
Moreover, it is generally inevitable in conventional centrifugation and expression operations that a certain amount of interfacing components will remain incompletely separated, at least in so far as being incapable of complete separation and pure collection after a single centrifugal process, as for example when a quantity of red blood cells will remain with the buffy coat after expression. Thus, conventional whole blood to buffy coat to platelet processing usually includes further processing steps after the initial whole blood separation process. This often includes at least four post-donation, post-initial separation processes/steps; namely; pooling of a plurality of buffy coats, then centrifugation of these pooled buffy coats, then expressing of the plasma and/or platelets therefrom and usually also a leukoreduction step. These tasks are generally carried out with manual, labor-intensive steps and blood centers are challenged with time-consuming, error-prone manual operations for such buffy coat processing, and these processes with their associated risks are in addition to the initial manual processing problems such as the inadvertent re-mixing as suggested above.
Still further, successful modern blood component therapy is dependent on high purity blood component fractions, i.e. these components should be contaminated as little as possible by each other. Particularly troublesome is contamination of any component product by the intermediate buffy coat fraction which contains the potentially contaminated white blood cells that would or could in turn contaminate the other interfacing component product or products. Controlled expression of the various fractions from the separation container to thereby reduce any re-mixing of the buffy coat with any other product has thus presented a fairly important, if not critical operation with respect to the achievement of pure or substantially pure end component products.
Thus, different techniques of achieving high purity separated fractions have been contemplated. Some suggestions have involved the use of a centrifuge rotor having an annular separation area for holding a generally annularly or ring-shaped separation container. Such a centrifuge may have provided for subjecting such a separation container to compression forces in the separation compartment of the rotor during centrifugal rotation to force fluids disposed therein to flow generally out of the ring container, and thus one or more of the separated layers may then have been pressed out and toward a central compartment of the rotor and into one or more secondary containers disposed therein even while they remain subjected to the prevailing centrifugal force field. Even so, success with such ring-shaped separation containers and centrally disposed secondary containers has heretofore been limited.